Now, in a bid to keep the species alive, embryos have been created using frozen sperm from dead northern white rhino males. The sperm was used to fertilise eggs from southern white females, a closely related species with a much healthier population count.

The resulting hybrid embryos have been frozen for implantation into surrogate mothers.

The two surviving members of the northern white species - a mother and daughter called Najin and Fatu who live in Kenya's Ol Pejeta Conservancy - cannot bear offspring, which is why a southern white surrogate is needed.

Image:Sudan died of an 'age-related complication' in March

It will also be a race against time, according to Thomas Hildebrandt, head of reproduction management at the Leibniz Institute for Zoo and Wildlife Research in Berlin.

He said: "Taking into account 16 months (of) pregnancy, we have a little more than a year to have a successful implantation."

Mr Hildebrandt hopes the first northern white rhino calf will be born in about three years, saying: "We are quite confident with the technology we have developed."

Some experts have warned it could already be too late, however.

Richard Kock, a conservationist at Britain's Royal Veterinary College, said: "I have no doubt that its purely scientific merit is laudable and it might have some application to endangered species conservation in the future, but I am afraid it is very much Nero fiddling after Rome is burning with respect to (northern) white rhino."

But Mr Hildebrandt stood by the effort, saying: "The northern white rhino didn't fail in evolution.

"It failed because it's not bulletproof.

"It was slaughtered by criminals which went for the horn because the horn costs more than gold."

He said that the disappearance of the northern white rhino, due to conflict and poaching, had left an ecological void but that scientists "have the tools in our hands to correct that".